Tank you Sezare56 for pointing out my approximations!
First of all, I really didn't know about theoretical neutral res position of A4. Where can I see documentation about that? I thought best position to be neutral il Filt1 at maximum frequency and minimum resonance. So my 1st test isn't good. I made it again and again with your setting, with better results, but not perfect at all. Then I tried with those settings:
Filt1: Frq max, res 57
Filt2 as a LowPass 2 poles: freq max, res 0. That was the best matching result, sonically and visually (1st picture).
What do you mean by "I suppose you used the Ext In setting"? Is it a setting memory? I just received Analog4 and I didn't see that in manual. But I understood a real test needs to bypass filters. So I used Fx Track and passed Se1 that way (because first test was made using Ext in as an oscillator). Results are way better (2nd picture), but not perfect in comparison with SE1 directly plugged in the soundcard (3rd picture). That pointed out one evidence : first terrible bass problem result is not due to for example an output HiPass DC offset, but it's more like some said a filter problem.
It doesn't seem easy to get a clean signal and then filter it?
I first made those tests because I was very disappointed of rough waveforms when comparing with other analog gear. My principal concern is to get nice Saw and Square without having to boost lo end with HiPass and res (I choose that machine to use both filter, not to compense problems with those filters).
Now, my goal is to achieve internal best Saw and Square, without loosing the filters. Every trick is welcome.